Bash Script rename file to modified day and add suffix

| Filename | DateModified | After Rename |
| --- | --- | --- |
| aaa.mp3 | 20230114 | 20230114_1.mp3 |
| bbb.mp3 | 20230113 | 20230113_1.mp3 |
| ccc.mp3 | 20230114 | 20230114_2.mp3 |
| ddd.mp3 | 20221205 | 20221205_1.mp3 |
| eee.mp3 | 20230113 | 20230113_2.mp3 |

I have a folder "/volume1/music/" with multiple random named mp3 file inside.

I want to rename file to date modified and add inscrease suffix to advoid same name.

I use the code below but don't know how to handle the counter suffix

cd "/volume1/music/"
counter=1
for file in *.mp3; do
    cdate=$(date -r "$file" +"%Y%m%d")
        echo "$cdate"
        if [ -f "$cdate" ]; then
            set counter=counter+1
        else 
            set counter=0
        fi
    echo mv "$file" "$cdate"_"$counter"
done

Thank you for your help!

Just move the counter initialisation inside the loop, and increment by repeatedly testing existence of full name rather than just date string.

You can add a test to avoid renaming files that already have the correct name format.

cd "/volume1/music/"

for oldfile in *.mp3; do
    cdate=$(date -r "$oldfile" +"%Y%m%d")
    echo "$cdate"

    if [[ $oldfile =~ ^[0-9]{8}_[0-9]{1,}\.mp3$ ]]; then
        if [[ $oldfile =~ ^"$cdate" ]]; then
            echo "skipping $oldfile"
            continue
        fi
    fi

    counter=1
    while
        newfile="${cdate}_${counter}.mp3"
        [ -e "$newfile" ]
    do
        (( counter++ ))
    done

    echo mv "$oldfile" "$newfile"
done